Two-sided, or dual-sided, direct thermal printing of documents such as transaction documents and receipts is described in U.S. Pat. Nos. 6,784,906 and 6,759,366, which are hereby incorporated by reference herein. In dual-sided direct thermal printing, the printers are configured to allow concurrent printing on both sides of thermal media or image elements moving along a feed path through the printer. In such printers a direct thermal print head is disposed on each side of the media along the feed path. In operation each thermal print head faces an opposing platen across the media from the respective print head.
In direct thermal printing, a thermal print head selectively applies heat to paper or other sheet media comprising a substrate with a thermally sensitive coating. The coating changes color or is imaged when heat is applied, by which “printing” is provided on the coated substrate. For dual-sided direct thermal printing, the sheet media substrate may be coated on, and heated from, both sides.
Many industries produce products that to some degree are sensitive to heat and/or UV exposure and/or that degrade to an unacceptable extent when exposed to excessive heat and/or UV radiation. One such example is the beverage industry, including alcoholic, non-alcoholic, refrigerated, and non-refrigerated beverages. Another example is the pharmaceutical industry wherein many medications lose their potency or their effectiveness when exposed to adverse environmental conditions such as excessive heat or UV radiation. Such industries would benefit from a system to identify products that have been exposed to excessive heat and/or UV radiation.